The present invention relates generally to techniques for semiconductor lasers. For example, the invention relates to techniques in which two or more beams of coherent light are emitted, such as from different active regions of a laser structure.
Various techniques have been proposed for multiple lasers or multi-beam lasers, and many such techniques are concerned with optical, electrical, and thermal interactions. U.S. Pat. No. 6,052,399, for example, describes an independently addressable laser array in which a high density, edge emitting laser array structure has native oxide layers formed in adjacent grooves in a p-cladding layer; the native oxide layers provide optical confinement and electrical isolation. U.S. Pat. No. 5,513,200 similarly describes a monolithic array of independently addressable diode lasers that are closely spaced but have low thermal, electrical, and optical crosstalk; an isolation groove is formed between adjacent laser elements, which are defined by rib loaded waveguides created by etching mesas above a planar active multilayer waveguide. U.S. Pat. No. 6,744,800 describes nitride based laser diode arrays on an insulating substrate, with contact layouts that reduce electrical and thermal crosstalk between laser diodes; buried layers are used to provide compact and low crosstalk contact structures. U.S. Pat. Nos. 4,870,652 and 4,980,893 both describe monolithic high density arrays of independently addressable semiconductor laser sources in which laser emitters or elements can be in close center-to-center proximity, e.g. on 3-10 μm centers, without undesirable phase locking and with minimal electrical and thermal interaction or crosstalk between independently addressed lasing elements.
Previous techniques, however, are limited in the ways they deal with optical interactions. It would be advantageous to have additional techniques for semiconductor laser structures, and, more specifically, it would be advantageous to have additional techniques that can be applied to alleviate optical interaction problems.